双光子顶点在Dirac材料非线性响应中的主导作用
Dominant Role of Two-Photon Vertex in Nonlinear Response of Dirac Materials
摘要：
利用守恒的Baym-Kadanoff方法，我们提出了一个完全令人信服的理论，在无序散射的存在下，非线性直流响应的狄拉克系统的电场。我们发现，非线性项是惊人的统治由一个占主导地位的双光子顶点，这是缺席裸水平和有限的，即使在弱耦合限制的外观。这种双光子顶点自生成突出了非线性区域中散射率的频率和场依赖性的关键作用。我们的研究揭示了狄拉克材料的非线性响应中的一种新的多体机制，其效应预计是可观察的。
英文摘要：
Using a conserving Baym-Kadanoff approach, we present a fully compelling theory of nonlinear dc response of a Dirac system to electric fields in the presence of disorder scattering. We show that the nonlinear terms are strikingly ruled by the appearance of a dominant two-photon vertex which is absent at the bare level and finite even in the weak-coupling limit. Such two-photon vertex self-generation highlights the crucial role of the frequency and field dependence of the scattering rates in the nonlinear regime. Our study reveals a novel many-body mechanism in the nonlinear response of Dirac materials whose effects are predicted to be observable.
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